using System;
using ch.ethz.ssh2.crypto.digest;
using Org.BouncyCastle.Math;
namespace ch.ethz.ssh2.crypto
{
	
	/// <summary> Establishes key material for iv/key/mac (both directions).
	/// 
	/// </summary>
	/// <author>  Christian Plattner
	/// </author>
	/// <version>  2.50, 03/15/10
	/// </version>
	public class KeyMaterial
	{
		public byte[] initial_iv_client_to_server;
		public byte[] initial_iv_server_to_client;
		public byte[] enc_key_client_to_server;
		public byte[] enc_key_server_to_client;
		public byte[] integrity_key_client_to_server;
		public byte[] integrity_key_server_to_client;
		
		private static byte[] calculateKey(HashForSSH2Types sh, BigInteger K, byte[] H, byte type, byte[] SessionID, int keyLength)
		{
			byte[] res = new byte[keyLength];
			
			int dglen = sh.DigestLength;
			int numRounds = (keyLength + dglen - 1) / dglen;
			
			byte[][] tmp = new byte[numRounds][];
			
			sh.reset();
			sh.updateBigInt(K);
			sh.updateBytes(H);
			sh.updateByte(type);
			sh.updateBytes(SessionID);
			
			tmp[0] = sh.getDigest();
			
			int off = 0;
			int produced = System.Math.Min(dglen, keyLength);
			
			Array.Copy(tmp[0], 0, res, off, produced);
			
			keyLength -= produced;
			off += produced;
			
			for (int i = 1; i < numRounds; i++)
			{
				sh.updateBigInt(K);
				sh.updateBytes(H);
				
				for (int j = 0; j < i; j++)
					sh.updateBytes(tmp[j]);
				
				tmp[i] = sh.getDigest();
				
				produced = System.Math.Min(dglen, keyLength);
				Array.Copy(tmp[i], 0, res, off, produced);
				keyLength -= produced;
				off += produced;
			}
			
			return res;
		}
		
		public static KeyMaterial create(System.String hashType, byte[] H, BigInteger K, byte[] SessionID, int keyLengthCS, int blockSizeCS, int macLengthCS, int keyLengthSC, int blockSizeSC, int macLengthSC)
		{
			KeyMaterial km = new KeyMaterial();
			
			HashForSSH2Types sh = new HashForSSH2Types(hashType);
			
			km.initial_iv_client_to_server = calculateKey(sh, K, H, (byte) 'A', SessionID, blockSizeCS);
			
			km.initial_iv_server_to_client = calculateKey(sh, K, H, (byte) 'B', SessionID, blockSizeSC);
			
			km.enc_key_client_to_server = calculateKey(sh, K, H, (byte) 'C', SessionID, keyLengthCS);
			
			km.enc_key_server_to_client = calculateKey(sh, K, H, (byte) 'D', SessionID, keyLengthSC);
			
			km.integrity_key_client_to_server = calculateKey(sh, K, H, (byte) 'E', SessionID, macLengthCS);
			
			km.integrity_key_server_to_client = calculateKey(sh, K, H, (byte) 'F', SessionID, macLengthSC);
			
			return km;
		}
	}
}